Apparatus for railway train communication systems



July 27, 1937.

| D. WHITELOCK ET AL. 88,

APPARATUSZ'FOR RAILWAY TRAIN COMMUNICATION SYSTEMS Filed May 2, 1936 T0iVayse'ae Sz 'gmaklppgafus I 1- 1 r 4 E: r m :5 7 a: [2: 9 4 Ll 4 Pl 17'11 9 262g 27 v T v N 54 N 53 4 50 a;

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INVENTORS Leland D. Whilelocig and Paul NBOJJIJPLL.

THE/l2 ATTORNEY Patented July 27, 1937 iJNl'lED stares earner series.

APPARATUS FOR RAHLWAY TRAIN C'OMlVIU- NIGATIQN SYSTEMS Leland l).Whiteleck, Wilkinsburg, and Paul N. Bossart, Cheswick, Fa, assignors toThe Union Switch & Signal Company, Swissvale, Pa., a corporation ofPennsylvania Application May 2, 1936, Serial No. 77,576

9 Claims. (Cl. 246-8) Our invention relates to apparatus for railwayabout these line wires Ll, L2, L3 and L4 in contrain communicationsystems, and has for an nection .with the present invention is the factobject the provision of novel and improved trackthat they provide asectionalized line wire ex Way apparatus for use in systems forcommunitending the full length of a designated stretch 5 cation betweentwo spaced locations on a train, of railway.

or between two different trains, or between a To form these successiveline wires into a wayside station and a train. communication channelwhich may be utilized We will describe three forms of apparatus emfortransmitting a communication current along bodying our invention, andwill then point out the the railway independent of the Wayside signalnovel features thereof in claims. system and without interference in anyway with 10 In the accompanying drawing, Fig. 1 is a diathe waysidesignal system, we provide a track grammatic view of one form. ofapparatus emcircuit network and a circuit connection at sebodying ourinvention wherewith existing line lected points. Through the medium ofsuch wires employed in a wayside signal system are track circuitnetworks and circuit connections,

5 made to form a channel for transmitting comeach individual line wireand the rails of the munication currentalong a railway. Fig. 2 is 2.associated track section in multiple are made to diagrammatic View of asecond form of appaform a closed circuit, and the successive circuitsratus embodying our invention wherewith exthus formed are coupled togetprovide isting line wires of a waysidesignal system are channeleffective to transmit the communication made to form a channel forcommunication cur current. When a track circuit network and cire 20rent. Fig. 3 is a diagrammatic view of appacuit connection are placed ata signal location, ratus embodying our invention wherewith a line thenetwork ordinarily spans the insulated rail which extends continuouslyalong a stretch of joints at that location. It will be understood,railway is made to form a channel for communihowever, that a trackcircuit network and circation current. cuit connection may be placed atlocations other 25 In each of several views, like reference than atinsulated rail joint locations if desired. characters designate similarparts. These track circuit networks and circuit con- Referring to Fig.1, the reference characters la nections are proportioned and adjusted totune. and lb designate the track rails of a railway the circuits formedthereby and to reduce the track and which are divided by the usualinsucharacteristic impedance as low as practicable 30 lated rail joints2 to form successive track secat the frequencies of the communicationcurtions, two full sections AB and BC and the rent Without endangeringthe integrity of the ends of the two sections adjacent thereto beingwayside signal circuits nor giving an excessive shown in Fig. 1. Thesetrack sections are those value of attenuation to the line wire andcirprovided for the usual wayside signal system, cuit connections. andit will be understood the entire railway may Looking at location A ofFig. 1, the circuit netbe divided into consecutive track sections, theWork comp W resistors 3 and 4, resistor 3 junction of each two sectionsbeing a. signal ing connected across the rails at the right-handlocation for the apparatus of a wayside signal side of the insulatedrail joints 2, and the resistor y T e reference characters Ll L2, L3,and 4 being connected across the rails at the left-hand 40 L4designateline wires each of which forms one side of the insulated railjoints. The mid-termiside of a signal control circuit extending the nalof resistor 3 is connected with line wire L2 length of the associatedtrack section and termiextending to the right from location A by acirnating in wayside signal apparatus at the ascuit connection includingwire 5, condenser 6,and sociated signal locations. For example, theseWire 7. In like manner, a circuit connection inline wires may each formone side of an apcluding wire 3, condenser 9, and. wire! connects preachlighting circuit for a wayside signal systhe mid-terminal of resistor 4to the line wire Ll tern. Looking .at location B of Fig. 1, the relayextending to the left from location A. The re- Eiil be an approachlighting relay controlled sisters 3 and 4 are each proportioned to 51)cver'a control circuit including a contact 83 of stantially match thecharacteristic impedance of a track relay (not shown) at location A andthe the rails at the frequency of the communication line wire L2. Theremaining portion of these current, and at the same time not impair thesignal control circuits is not shown for the Wayside signal circuits.For example, the comsake of simplicity since such circuits formv no munia n Current y be a carrier telephone part of our invention. Thesignificant feature current of 7500 to 9500 cycles per second. That is,55

the telephone current may be the upper side band of a carrier of 7000cycles modulated at voice frequencies extending from 500 to 2580 cyclesper second. We have found that resistors 3 and 4, when of about 10 ohmseach, will substantially match the characteristic impedance of the railsat the frequency range cited above under the usual ballast resistanceconditions. Such resistors are also large enough to not seriouslyinterfere with the usual track circuits of the wayside signal system.Condensers 6 and Q interposed in the circuit connections when made about0.25 microfarad are satisfactory to efiiciently tune at the frequency ofthe communication current a line wire which forms one side of a signalcontrol circuit for a typical block length.

At location B of Fig. 1, the circuit network is similar to that justdescribed for location A except the resistors l3 and 33 which areconnected across rails at the opposite sides of the insulated railjoints, are joined at their mid-terminals by a conductor 34. Themid-terminal of resistor i3 is connected with line wire L2 extending tothe left from location B over a connection including wire 36, condenser52, and wire ii; and the midterminal of resistor 33 is connected withline wire L3 over a circuit connection including wire 38, condenser w,and wire 4 I.

At location C, the track circuit network and circuit connections forconnecting the line wires L3 and LA with the track rails of therespective track sections are the same as at location B except for thefact a condenser 35 is interposed in the conductor 3'! joining themid-terminals of the resistors 39 and 43. It is to be seen that eachtrack section of Fig. 1 is provided with a closed circuit one side ofwhich is formed by the two track rails in multiple, and the other sideof which is formed by a line wire. Hence, carrier telephone currentsupplied to the two rails of section AB in multiple flows in a circuitthat may be traced from the point where it is supplied to the rails toresistor 3, the two portions of resistor 3 to its mid-terminal, wire 5,condenser 6, wire 1, line wire L2, wire I l, condenser 12, wire 35 tothe midterminal of resistor l3, the two portions of resistor 13 to thetrack rails la and lb, and, thence, to the starting point. Likewise, asimilar circuit may be traced for section BC, and for each of theremaining sections of the railway.

Assuming a communication current of the frequency range explainedhereinbefore is supplied to the track rail of section A-B and flows inthe circuit just traced for that section, during onehalf cycle of thecurrent, the potential of the mid-terminal of resistor I3 is aboveground po-. .tential, and during the other half cycle, its potential isbelow ground potential due to the distributed ballast resistance of thetrack rails. Communication current is transferred from the above-tracedcircuit of section A-B to the circuitforthe section BC by virtue of thevariations in the potential of the mid-terminal of resistor 58 withrespect to ground potential. 'For example, when the potential of themid-terminal of resistor i3 is above ground potential, current flowsover conductor 34 to the mid-terminal of resistor 33, and, thence, toground over two parallel paths One of which includes wire 38, condenser43, wire 3 8, line wire L3, circuit connection including condenser 42 atthe right-hand end of section BC, the two portions of resistor and therails of section BC serving as a ground electrode. The other pathincludes the two portions of resistor 33 and the rails of section BCserving as a ground electrode. During the other half cycle of thecurrent, current flows from ground to the midterminal of resistor isthrough the medium of the circuit of section BC. Hence, communicationcurrent supplie to the rails of section A-B flows in a permanentlyclosed circuit of which the line wire L2 forms the return side of thecircuit, and communication current is transferred to the rails of thesection BC through the medium of the corresponding circuit for thatsection. The current thus transferred is available for influencingreceiving apparatus coupled with the track rails of section BC. Becauseof the frequency range of the communication current and due to theproportioning of the parts of the closed circuits of the respectivetrack sections, the wayside signal circuits associated with these tracksections are not effectively influenced. It is to be noted that atlocation A, transfer of communication current from the section AB to thesection to the left of location A takes place when the insulated railjoints at location A are short circuited by a train. At location C, thecondenser 35 interposed in the track circuit network tunes the track tomaximum efiiciency of the frequency range of the communication current.This condenser should be about two microfarads.

Three different forms of track circuit networks are disclosed in Fig. l,and it will be understood that any one of these three forms may beprovided at each signal location, if desired. It is to be noted that ata location other than an insulated rail joint location the track circuitnetwork would consist of a single resistor such as resistor 55 would beconnected with the line wires leading in each direction from thatlocation over a circuit connection similar to those described for InFig. 2, the track rails Ia and iii are divided into track sections thesame as in Fig. 1, three full sections Ai-Bi, BiCi, and C!-Di beingshown in the drawing. The line wires L5, L55, LT,'L8, and L9 are eachone side of a signal control circuit associated with the respectivetrack sections. For example, these line wires may each be included in anapproach lighting control circuit the same as in Fig. 1. The adjacentends of these respective line wires are joined through two condensersconnected in series. For example, at location Al, line wires L5 and L6are connected through condensers ll and !8 in series. These condensersii and it are included the circuit connection which connects the linewires L5 and L5 with the track circuit network at that location. Threepossible arrangements for the track circuit network are disclosed inFig. 2. At location At, the resistors i4 and i5, which are connectedacross the track rails at the opposite sides of the insulated railjoints, are joined at their mid-terminals by a conductor it. Themidterminal of condensers i? and i8 is connected with the conductor 16over a circuit connection including wire It, condenser 25 resistor 24,and wire 22. At location Bi, the track circuit network is the same as atlocation A! and includes resistors 23 and 2c connected across the railsof the respective track sections, and a conductor 25, joining themid-terminals of resistors 22: and 2d. at location Bi is connected withthe conductor 25 of the track circuit network over a connectionincluding wire 28, resistor 29, and wire 3%. At location Ci, thearrangement is the same as at location AI, except a condenser lfil isinterposed at location A, and its mid terminal The mid-terminal ofcondensers 2'3 and El in the conductor joining the mid-terminals of theresistors connected across the rails. At location DE, the arrangementdiffers from that at location Cl in that two condensers 3i and 32 areserially interposed in the conductor joining the mid-terminals of theresistors connected across the rails,

and the circuit connection by which the line acteristic impedance of therails at the frequency of the communication current the same as inFig. 1. Th condensers interposed in series with the sectionalized linewire are each proportioned to series tune the line wire and are eachabout 0.25 microfarad in a typical case. We have found that when seriestuning is employed, two condensers one at each end of the line wire aremore effective than where only one condenser is provided. Thearrangement in Fig. 2 difiers from that of Fig. 1 in that the resultingcommunication channel consisting of the sectionalized line Wire as oneside and the track railsas the other side, is loaded to reduce itscharacteristic impedance to more nearly match the rails by virtue ofcoupling condensers and/or resistors. For example, condenser at locationAl is proportioned to load the two circuits extending in the oppositedirections from that location to reduce their characteristic impedance,vand it is also effective to couple the two circuits. At location Bl, theresistor 29 is proportioned to reduce the characteristic impedance ofthe circuits'extending in opposite directions from that location, and italso serves as a coupling unit between the two circuits. The condenser20 should be about one microfarad and the resistor 29 should be aboutohms. The resistor 2| atlocation Al and resistors 5c and at locations CIand Di, respectively, are provided to avoid a possible false operationof the wayside signal system in the case of a broken rail. A value of 10ohms has been found satisfactory for these resistors in conjunction witha circuit condenser or condensers.

Communication current supplied to the track rails of section Al-Bl inmultiple flows in a circuit which may be traced to the left from thepoint where the current is sup-plied to the rails, the two portions ofresistor R5 to itsmid-terminal, wire 22, resistor 2i, condenser 20, wirel9, condenser I8, line wire L6, condenser 26, wire 28, resistor 29, wire30, conductor 25 to the midterminal of resistor 23, the two portions ofresistor 23 to the rails la and l b, and back to the original point. Dueto communication current flowing in this circuit, the potential. of themidterminal of resistor 23 varies with respect to ground potential andcommunication current is transferred to the circuit associated with thesection Bl-Cl in the samemanner as described for Fig. 1. In addition,the voltage drop across resistor 29 also causes communicationcurrent toflow in the closed circuit associated with the section BlCl.Consequently, communication current supplied to the rails of sectionAlBl is transferred to the corresponding circuit associated with sectionBICI and, in turn, to the corresponding circuits of the sections moreremote.

In Fig. 3, the track rails to and lb are insulated into track sectionsAZ-BZ and BZ--C2. Track circuit networks are provided at each of thelocations A2, B2, and C2. As here shown, these networks are each similarto the network provided at location Dl of Fig. 2, and it is thought tobe unnecessary to repeat their description in detail. In this case, theline wire Llli is common to all track sections and does not terminate ateach signal location. The line wire Llll may, for example, be one sideof anexisting power line common to all signal locations of the waysidesignal system. The circuit connections between the track circuitnetworks and the line wire Llfi includein each case a coupling condenserand a resistor; For example, at location A2, the network is connectedwith the line wire'Llil, over wire 46, resistor ll, condenser 48, andwire 49. The resistors 41, 50, and 5| at the respective locations A2,B2, and C2 are provided to prevent a possible false operation of thewayside signal system in the case of a broken rail. In Fig. 3, thecondensers 48, 52, and 53 are each proportioned to reduce the impedanceof the adjacent section of the line wire Lil) at the frequency of thecommunication current. It follows thateach track section of Fig. 3 isprovided with a permanently closed circuit one side of which is formedby the two track rails in multiple, and the other side of which isformed by a section of the line wire LEO. Communicationcurrent suppliedto the rails of a track section flows in the closed circuit associatedwith that track section and is transferred to the closed circuits forthe adjacent track sections in the same manner as described in Figs. 1and 2.

It is to be noted that in practicing our invention, the apparatus islocated at signal locations and no additional connections to the railsother than the existing track leads are required. Furthermore, allapparatus may be housed in the existing housing provided for the usualwayside signal systems.

Although we have described only three forms of apparatus embodying ourinvention, it is under- 7 stood that various changes and modificationsmay be made therein within the scope of the ap- .the characteristicimpedance of the track rails at the frequency of the communicationcurrent, a line wire extending along the railway, and a circuitconnection for each network to connect a mid-terminal of the resistorwith the line wire and including a reactance proportioned to tune theassociated section of the line wire at'the frequency of thecommunication current to provide a resulting communication channeleffective to transmit communication current supplied to the rails at anypoint along the railway in both directions.

2. Trackway apparatus for use in connection with railway communicationsystems for cornmunicationbetween apoint on a train and a re mote point,comprising in combination with the usual insulated track sections, acircuit network at each junction of adjacent track sections consistingof resistors one connected across the rails of each of the two adjacentsections and a conductor joining the mid-terminals of the resistors,said networks each proportioned to match the characteristic impedance ofthe track rails at the frequency of the communication current, a linewire extending along the railway, and a circuit connection for eachnetwork to connect its conductor with said line Wire and including acondenser proportioned to tune the line wire at the frequency of thecommunication current, whereby a series of permanently closed circuitsis provided with the individual circuits coupled to the adjacentcircuits for transmitting communication current supplied to the rails ofany one of the track sections to the rails of the adjacent sections.

3. Trackway apparatus for use in connection with railway communicationsystems for communication between a point on a train and a remote point,comprising in combination with the usual insulated track sections andexisting signal control line wires one wire extending along eachsection, a circuit network at each junction of adjacent track sectionsconsisting of two resistors one connected across the rails of each ofthe adjacent sections and a conductor connected between themid-terminals of the resistors, and circuit connecting means at each ofsaid junctions to separately connect the two line wiresextending inopposite directions from the junction with the conductor of theassociated network to form a closed circuit for each track section whichconsists of the two rails in multiple as one side and the line wire asthe other side, and each of said circuit connecting means pacitanceproportioned to tune each of the adjacent circuits at the frequency of acommunication current and to couple the adjacent circuits.

4. Trackway apparatus for use in connection with railway communicationsystems for communication between a point on a train and a remote point,comprising in combination with the usual insulated track sections andexisting signal control line wires one wire extending along eachsection, a circuit network at each junction of adjacent track sectionsconsisting of two resistors onev connected across the rails of each ofthe adjacent sections and a conductor connected between themid-terminals of the resistors, means at each junction to connect theadjacent line wires and including two condensers in series, saidcondensers each proportioned to tune the associated line wire at thefrequency of the communication current, and a circuit connection at eachjunction to connect the mid-terminal of said two condensers at thatjunction with the conductor of the network at the same junction.

5. Trackway apparatus for use in connection with railway communicationsystems for communication between a point on a train and a remote point,comprising in combination with the usual insulated track sections and anexisting line wire extending along each section to form one side of aparticular control circuit; a circuit network at each junction ofadjacent track sections including a resistor connected across the railsof each of the two adjacent sections, a conductor joining themid-terminals of the two r-esisters and two condensers seriallyinterposed in said conductor; and circuit means at each junctionincluding two condensers serially connected between the adjacent linewires and an imincluding capedance element connected between the midterminal of these two condense-rs and the midterminal of the twocondensers of the circuit network at the same junction.

6. Trackway apparatus for use in connection with railway communicationsystems for communication between a point on a. train and a remotepoint, comprising'in combination with the usual insulated-track sectionsand an existing line wire extending'along each section to form one sideof a particular control circuit; a circuit means at each junction of thetrack sections connected to the adjacent two line wires and includingtwo condensers in series, a. circuit connection at each of saidjunctions for connecting the'mid-terminal of the tWo condensers of theassociated circuit means with the rails in multiple of each of the tracksections adjacent the same junction to form a closed circuit for eachtrack section, and a coupling condenser interposed in each circuitconnection whereby communication current supplied to the rails of ase-ction'flows in the closed circuit for that section independent of thecontrol circuit of which the associated line wire is a part and istransferred to the closed circuits of the adjacent track sections byvirtue of the coupling condenser.

7. Trackway apparatus for use in connection with railway communicationsystems for communication between a point on a. train and a remotepoint, comprising in combination with the usual insulated track sectionand a line wire extending along the section, an impedance connectedacross the rails at each end of the section, said impedancesproportionedto match the characteristic impedance of the two rails of the section inmultiple at the frequency of the communication current, a circuitconnection at each end of the section to connect the mid-terminal of theassociated impedance with the line wire to .form a permanently closedcircuit consisting of the two rails in multiple as one side and the linewire as the other side, and another impedai ce interposed in each ofsaid circuit connections and said other impedances each proportioned tomatch the impedance of the line wire. for the communication current.

8. Trackway apparatus for use in connection with railway communicationsystems for communication between a point on a train and a remote point,comprising in combination with the usual insulated track section and anexisting line wire extending along the section to form one side of aparticular control circuit, a resistor connected across the rails ateach end of the section, said resistors proportioned to match thecharacteristic impedance of the two rails of the section in multiple atthe frequency of the communication current, and a circuit connectionincluding a condenser at each end of the section to connect themid-terminal of the associated resistor with the line wire to form apermanently closed circuit consisting of the two rails in multiple asone side and the line wire as the other side and which circuit isindependent of said control circuit, and said condensers proportioned totune out the reactance of the line wire for the communication current.

9. Trackway apparatus for use in connection with railway communicationsystems for commuhication between a point on a train and a remote point,comprising in combination with the usual insulated track sections andexisting signal control line wires one Wire extending along eachsection, a circuit network at each junction of adjacent tracksectionsconsisting of two resistors one connected across the rails ofeach of the adjacent sections and a conductor connected between themid-terminals of the resistors, and a circuit connection for eachnetwork to connect its conductor to the two line wires extending inopposite directions from the junction, and including capacitanceproportioned to effect a predetermined characteristic impedance for eachof the associated line wires at the frequency of the communicationcurrent to provide a resulting communication channel efiective totransmit communication current supplied to the rails of a track sectionto the rails of the adjacent sections.

LELAND D. WHITELOCK. PAUL N. BOSSART.

